Ignore a file when merging -- but include it in pushes

Question

I have a django project and I'm using git.

I need to have different settings.py file, for each branch.

I've tested add settings.py to .gitattributes with merge=ours, but it not worked because if it's not having any conflict Git will merge normally.

Also, add settings.py to .gitignore is not an option, cause if I change something in the settings.py, I want it pushed to the same branch.

Is there a way to ignore a file when merging but still push it?

UPDATE:

I've tried VonC's solution and I've created two settings: settings_production.py and settings_development.py.

So, I pip installed gitpython and used it in my settings.py, like this:

from git import Repo
import os

r = Repo(os.path.realpath(os.path.dirname(__file__)))
if r.active_branch.__str__( == 'master':
    from settings_production.py import *
else:
    from settings_development.py import *

And it worked fine.

Answer 1

I prefer having versioned:

• a template file settings.py.tpl
• a value file per branch: settings.py.branch1 in branch1, settings.py.branch2 in branch2, ... (meaning, no merge issue ever: each value file remains untouched)
• a script able to detect the current branch, take the right value file and build from the template file the final settings.py (which is private to your working tree: it is never versioned)

That script can be automatically called through a content filter driver which will, on checkout, build the right config file.

A .gitattributes file can register that 'smudge' script for the settings.py.* files.
(no need for a 'clean' script on checkin)